Curtain walls are the outer covering of a building in which the outer walls are non-structural, and merely keep the weather out and occupants of the building in the building. A curtain wall does not carry any dead load weight from the building other than its own dead load. In this context a dead load, or also commonly referred to as a static load, includes loads that are relatively constant over time, including the weight of the structure itself, and immovable features such as walls, plasterboard or carpet. Curtain walls are designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building and its own static load weight forces. Exterior wind loads combined with the curtain wall's own weight are transferred to the building through, for example, anchors at specific points of attachment. Curtain walls may be attached to anchors via different methods. Typical curtain wall assemblies include structural members called mullions which separate and secure the curtain wall panels. The mullions are secured to the building via curtain wall anchors. Curtain wall anchors are the connection means between the curtain wall mullions, to the building structure.
Typical building construction techniques with steel supported concrete floor slabs employ a bent steel plate fixed to spandrel beams as pour stops for concrete. The bent plate pour stops may also be referred to as edge angles. Considerable time is required at a steel fabricator to bend all of the plate to install as pour stops. The bent plate pour stops are then taken to the job site, positioned, and welded on top of the spandrel beams. Bent plates often provide a wavy edge of the slab with significant deviation of the actual edge from planed location. The deviation creates difficulties in attachment of a curtain wall while trying to maintain a controlled planar surface in the outer surface of the curtain wall. Additionally, the curtain wall is typically attached to the bent plate pour stop via clip angles welded to the pour stop or supporting beam. This requires considerable time and labor to position the curtain wall anchors and weld them in place. The welding also requires costly skilled laborers and adds significantly to the overall construction schedule.
Occasionally embedded anchor channels are specified for a building slab edge to allow for curtain wall attachment. These typically require cutting the steel pour stop and welding sections of anchor channels or block-outs for top mounted anchor channels in the concrete slab. Although these options allow for some adjustability for the curtain wall installation they still do not account for the wavy bent plate slab edge and they require significant coordination between construction trades in addition to being costly to install.
One of the concerns in using existing anchor channels welded to steel edge angles is that excessive loads can cause the edge angle to bend. Structural engineers are regularly confronted with this issue and by contractors who want easier/faster construction techniques. The disclosed curtain wall anchor system embodiments include options for providing a direct or indirect load path into the concrete slab or steel beam to prevent edge angle bending and provide faster, less costly construction.